Many modern computer systems implement various types of clustered architectures. In particular, the Parallel Sysplex clustered system offered by International Business Machines Corporation (IBM) (Parallel Sysplex and IBM are registered trademarks of International Business Machines Corporation, the present assignee hereof) comprise one or more S/390 servers coupled via intersystem links to one or more Coupling Facilities (CFs) which provide a structured, shared electronic storage for the coupled servers (S/390 is a registered trademark of IBM).
Establishment of a Parallel Sysplex computing system can be a work-intensive task which involves the acquisition and customization of new hardware and software. It has therefore been found advantageous to offer customers the opportunity to determine the benefits derived from the Parallel Sysplex system implementation by providing an emulated Parallel Sysplex computing environment for customer testing.
The foregoing problem has been previously addressed by providing a facility whereby the function of the Parallel Sysplex system can be emulated within a single hardware machine. In U.S. Pat. No. 5,564,040 to Kubala (assigned to the present assignee and incorporated herein by reference), the program code for performing the functions of the Coupling Facility is loaded into a maximum of two logical partitions of main storage in the hardware machine. In the Kubala patent, the (server mode) CF memory partitions are non-user accessible and provide Coupling Facility functions by interacting with user-accessible (non-server mode) memory partitions to simulate the function of a Parallel Sysplex system. While the Kubala patent does provide a simulated Parallel Sysplex system, it is limited to implementations including only two simulated Coupling Facilities and requires the allocation of a logical partition of main storage for each of these Coupling Facility instances.
In accordance with the foregoing it is clear that a solution which provides a customer with the ability to simulate highly complex Parallel Sysplex implementations including up to eight Coupling Facilities in a single Parallel Sysplex system, or alternatively to test multiple Parallel Sysplex systems on a single hardware machine without requiring the actual hardware systems or storage necessary for the real hardware-based implementation would prove advantageous to such customers. Moreover, it would be further beneficial to provide this simulated hardware function within a software environment having pre-existing debugging facilities with which the customer could more-effectively test the virtualized hardware implementation.
In response to these identified user requirements, via the facilities of the present invention, the services of the Coupling Facility or any other microcode-based hardware machine function can now be provided in a virtual machine of VM/ESA (VM), which is referred to as a virtual machine hypervisor or supervisor of other operating systems (VM/ESA is a registered trademark of IBM). Consequently, customers may test and debug the programs that are to use Coupling Facility services in a simulated Parallel Sysplex system comprising virtual machines rather than real machines.
This virtualization, by utilizing pageable storage, also allows unlimited multiple copies of the function to exist within a single computing system, each in its own virtual machine. Accordingly, the VM operating system allows a user to emulate one or more complete, independent simulated Parallel Sysplex systems, each with one or more CFs, in a single machine or logical partition thereof. This enables customer testing of large complex multisystem configurations without requiring those customers to acquire the actual hardware required for the configurations, or to possess the larger real storage required for such testing.
An additional advantage of implementing the simulated hardware machine function within the VM operating system is the availability within VM of existing debugging facilities and the ease of virtual machine re-configuration therein of this virtual Parallel Sysplex implementation. Users of the VM operating system have long utilized these facilities to test other software-based features, and accordingly this familiarity serves to aid in the testing of the virtual Parallel Sysplex system.